Flanged-pipe joints are desirable for a large number of industrial purposes and generally are formed between a pair of aligned pipes each of which is provided with a circular flange formed with a multiplicity of perforations or bores adapted to be traversed by respective bolts which draw the flanges together. A seal may be provided inwardly of the array of bores and the flanges outwardly of the seals are usually spaced apart to define a gap ensuring that the flanged ends of the pipes will bear tightly against the seals. In other words the confronting annular surfaces of the flanges are set back from the ends of the pipes which are to form the actual seal.
For replacement of such pipes, e.g. to change the seals or for reassembly or disassembly of a portion of an apparatus, it is necessary to separate the flanges at the joint. It may be desirable to insert disks, new sections of pipe in an existing line, or new pieces of apparatus provided with flanged fitting, to replace a burst pipe, to resurface a corroded sealing face or to replace a seal clamped in the pipe joint.
Such disconnection of a flanged-joint is not always simple since the pipes are generally held together with a high longitudinal force which may be generated by mounting of the lengths of pipe or flanged fittings tightly in place, because the assembly has been anchored in a mounting structure or simply to resist the forces which tend to break open the joint. Furthermore, corrosion may cause the flanged-joint to be locked against separation. The forces holding the joint together, in spite of removal of the bolts, are particularly pronounced when the pipes connect the flanged fittings of fixedly positioned vessels.
In order to separate the sections of pipe the flanged-joint it is known to drive a wedge into the gap between the flanges, the wedge generally being constituted of wood to prevent excessive damage to the flanges and their surfaces. However, in spite of considerable care, damage to the sealing surfaces frequently occurs. The damaged sealing surfaces cannot be reused and refirnishing of them is very expensive and can involve long downtime when the pipeline is part of an industrial establishment. The use of wedges which must be driven between the flanges of the joint also has the disadvantage that the technique may be dangerous to personnel in the vicinity since the wedge tends to fly out of the gap as it is being driven.
U.S. Pat. No. 2,358,651 describes a system for separating the flanges of a joint or changing the seals thereof which involves threading a screw into respective internally threaded bores of one of the flanges. Simply by screwing in the pressure bolts it is possible to urge the flanges apart so that the seal, which is received in a groove, can be replaced.
The disadvantage of this system is that separate bores within internal threads must be provided in the flanges so that the system cannot be used with conventional flanges and involves additional costs in the fabrication of such pipe flanges to accommodate the technique.
Another system is described in U.S. Pat. No. 3,393,795 in which a friction fitting is provided on the outer side of the flange and cooperates with a screw spindle also disposed laterally of the flanges. Because the system invariably tilts, the device has been found to be only limitedly successful.
U.S. Pat. No. 3,107,419 describes a hydraulic device in which a pair of grippers engage the flanges to be separated. This device has been found to be difficult to handle and to cause problems in use. Similar disadvantages also characterize rotary wedges between the flanges and lateral spindles driven into the gap between them.